Messages in this thread Patch in this message | | | Date | Sat, 18 Aug 2007 07:56:02 -0700 | From | Stephen Hemminger <> | Subject | Re: [PATCH] x86-64: memset optimization |
| |
On Sat, 18 Aug 2007 11:46:24 +0200 Andi Kleen <ak@suse.de> wrote:
> On Saturday 18 August 2007 01:34:46 Stephen Hemminger wrote: > > Optimize uses of memset with small constant offsets. > > This will generate smaller code, and avoid the slow rep/string instructions. > > Code copied from i386 with a little cleanup. > > > Newer gcc should do all this on its own. That is why I intentionally > didn't implement it on 64bit. > > On what compiler version did you see smaller code? > > -Andi >
The problem is that on x86-64 you are overriding memset() so the builtin version doesn't kick in. You allow gcc to inline memcpy but not memset.
What about adding code similar to memcpy() stuff.
--- a/include/asm-x86_64/string.h 2007-08-18 07:37:58.000000000 -0700 +++ b/include/asm-x86_64/string.h 2007-08-18 07:44:31.000000000 -0700 @@ -43,8 +43,13 @@ extern void *__memcpy(void *to, const vo __ret; }) #endif -#define __HAVE_ARCH_MEMSET -void *memset(void *s, int c, size_t n); +#define __HAVE_ARCH_MEMSET 1 +#if (__GNUC__ == 4 && __GNUC_MINOR__ >= 3) || __GNUC__ > 4 +extern void memset(void *s, int c, size_t n); +#else +#define memset(s, c, n) __builtin_memset((s),(c),(n)) +#endif + #define __HAVE_ARCH_MEMMOVE void * memmove(void * dest,const void *src,size_t count); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |